Integration of real-time planning and control in an unstructured manufacturing workcell

In this paper, we consider the problem of real-time planning and control of a robot manipulator in an unstructured workspace. The task we consider is to control the manipulator, such that the end-effector follows a path on an unknown surface, with the aid of a single Camera assumed to be uncalibrate d with respect to the robot coordinates. To accomplish a task of this kind; we propose a new control strategy based on multisensor fusion. We assume t hat three different sensors, i.e. encoders ;mounted at each joint of the ro bot with 6 d.o.f., a force-torque sensor mounted at the wrist of the manipu lator and a visual sensor milk a single camera fixed to the ceiling of the workcell, are available. Also, we assume that the contact point between the tool grasped by the end-effector and the surface is frictionless. To descr ibe the proposed algorithm that we have implemented. first of all we decoup le the vector space of control variables into two subspaces, and use one of the subspaces for controlling the magnitude of the contact force on the su rface and the other subspace for controlling the constrained motion on the surface. In this way the control synthesis problem is decoupled and we are able to develop a new scheme that utilizes sensor fusion to handle uncalibr ated parameters in the workcell and wherein the surface on which the task i s to be performed is assumed to be visible, but has an apriori unknown posi tion.